1. Field of the Invention
This invention relates to a power equipment having a device which detects any abnormality occurring within the power equipment. More particularly, it relates to a power equipment including an electromagnetic wave detection device which detects a partial discharge appearing within the power equipment.
2. Description of the Background Art
A power equipment, such as an oil-filled transformer or a gas-insulated switching equipment employed in a substation or the like, in which a high voltage conductor is supported by an insulator within an enclosed container, sometimes undergoes a partial discharge due to a cause such as the mixing of foreign matter or an inferior contact. When the partial discharge is let stand, the occurrence of a serious fault is apprehended. In order to prevent such a fault from occurring, accordingly, it is necessary to detect the partial discharge phenomenon early and to take a countermeasure.
From the viewpoint of prolonging the lifetimes of existing possessed facilities, it has recently been required of the electric power industry of electric power companies etc. to furnish each of the existing possessed facilities with a partial-discharge diagnosis device which can measure the electromagnetic wave of the partial discharge at a high sensitivity in the order of 10 pC (picocoulombs), for the purpose of detecting the partial discharge within the enclosed type power equipment.
In order to cope with the requirement, an antenna installation system for electromagnetic wave detection is considered. The antenna installation system has hitherto been adopted in a novel fabricated product, and it is such that an internal electrode and an internal antenna are disposed within the enclosed equipment. In the antenna installation system, however, a dedicated electric-field relaxation shield or the like needs to be disposed around the disposed sensor, and a large-scale remodeling site work is required, so that the actual adoption of the system is often impossible on account of a high cost. On the other hand, as a simple remodeling method having heretofore been known, it is considered to adopt a method wherein a signal is detected by clamping a CT or the like to the ground line of the equipment. Since, however, a signal excited by the external electromagnetic wave of radio broadcasting, TV broadcasting or the like flows through the ground line, only a measurement precision in the order of 1,000 to 10,000 pC is attained.
Meanwhile, a method wherein the electromagnetic wave generated by the partial discharge is detected by an antenna located outside the enclosed container is a “bushing-vicinity installation antenna system” wherein the antenna is arranged on that outer surface of a bushing which corresponds to the upper end of a shield disposed on the bushing (refer to, for example, Patent Document 1 being JP-A-2002-071743).
The antenna system disclosed in Patent Document 1 has the problem that a high-frequency signal as in the case of the partial discharge within the enclosed container is greatly attenuated in propagating from within the equipment to the exterior thereof. Another problem is that, since the antenna is located in an open space, it detects electromagnetic wave noise in the space. After all, an S/N (signal-to-noise) ratio lowers, and the detection at a desired high sensitivity is impossible.